All cells are able to monitor and make appropriate adaptive responses to changes in their environment. Such adaptive responses in bacteria are often regulated by a multi-component signal transducing system. When exposed to the appropriate stimuli, a sensory receptor, generally an inner membrane protein, is activated to autophosphorylate a histidine residue. This high energy phosphate is transferred from the histidine to an aspartate residue on the second protein in the regulatory cascade, the regulatory response protein. It is the phosphorylated regulatory response protein that then mediates the adaptive response either by interacting with DNA, altering transcription, or with a specific protein(s), altering its activity. In addition to regulation at the level of phosphorylation, the amount of phosphorylated regulatory response protein is further controlled by associated phosphatases.
Regulatory systems of this nature have been identified in over twelve diverse bacterial genera and have been found to regulate a variety of cellular processes including virulence and pathogenic determinants. (For a review see Bibliography entries 1,2). In Escherichia coli (E. coli), it is predicted that there may be 50 different pairs of signal transducing proteins. Some of these pairs include CheY, CheA and CheB, which are involved in the gliding versus tumbling response of bacteria in chemotaxis; PhoR and PhoB, which regulate phosphorus assimilation; and EnvZ and OmpR, which regulate outer membrane porin protein expression (2,3,4,5,6).
Bacteroides fragilis is the major anaerobic bacterium comprising the bowel flora of man. Bacteroides fragilis is also one of the major anaerobic bacteria isolated from anaerobic or mixed infections. As such, this bacterium produces various virulence factors which are involved in colonization and invasion of the organism. These factors include activities such as a nuraminidase.
This invention relates to the cloning and identification of a pair of signal transducing regulatory proteins cloned from Bacteroides fragilis, as well as to the phenotypes that expression of the regulatory proteins imparts upon E. coli.